Pads for grinding or polishing lens blanks have been known for quite some time. For example, U.S. Pat. No. 3,959,935 discloses a lens blank grinding pad comprising a pliable sheet of water-proof material (e.g., paper or fabric) with an adhesive coating on one side thereof for adhering said pad to the surface of a lens grinding or polishing lap or tool. This patent then suggests dispersing an abrasive substance, such as silicon carbide, on the surface of the pad, so as to permit a smooth fit over the curved working surface of the underlying tool.
While this prior U.S. patent contemplates that a prepolishing pad is first fitted to the working surface of the tool by suitable adhesion means, following which the grinding pad is then contact-adhered to the surface of the prepolishing pad, this disclosure does not contemplate distortion-free removal for later re-use, or for ease of repositioning adjustment prior to commencement of the grinding or polishing operation. As U.S. Pat. No. 3,959,935 states, at the top of Column 4, "Once used, the abrasive-impregnated pad is removed and another pad is used for grinding another lens blank."
For further background relating to this particular invention, see U.S. Pat. No. 4,086,068 issued Apr. 25, 1978, which discloses a configured lens grinding and polishing lap-cover. This patent recognized the same problems solved by the instant invention, but pursued an entirely different approach to the solution.
That is, this latter patent expressly noted that prior lap-covers could not be cleanly stripped in one piece from the lap surface, by merely detaching one portion of the lap-cover, then stripping off the entire cover. The '068 patent tackling the problem from the standpoint of utilizing something of a centipede-shaped pad whereby the side, appendage portions (legs) thereof did not tend to tear away as the leading end (or head) was stripped back towards the tail, or terminal end.
However, the pad or lap-cover configuration taught and claimed by this particular patent is severely restrictive in that it provides literally no freedom from the standpoint of pad design.
To be noted also, the pressure-sensitive adhesive suggested by the '068 patent for adhering its lap-cover directly to the working surface of the tool was 3M "Scotch" 442DCY double-coated tape. As is well known in the art, this is an extremely tacky, highly-adhesive material, which characteristic is readily confirmed by the '068 disclosure. That is, in order to cope with this type of difficulty-strippable adhesive, the '068 disclosure suggested that it was essential to redesign the pad itself. Opposed to the teachings of this patent, the instant invention approaches the problem by materially altering the characteristics of the adhesion system, thereby permitting unrestricted freedom of pad design.